One-Pot Synthesis of Menthol Starting from Citral over Ni Supported on Attapulgite-H-Beta-38 Extrudates in a Continuous Flow: Effect of Metal Location

Abstract

The one-pot synthesis of menthol from citral in a continuous mode was investigated over three different types of extrudates, namely Ni supported on H-Beta-38 and extruded with attapulgite, Ni supported on attapulgite and extruded with H-Beta-38, and the extrudates, which were shaped after deposition of Ni on both H-Beta-38 and attapulgite in the powder form. These composite catalysts were characterized by X-ray diffraction, transmission and scanning electron microscopy, temperature-programmed reduction of H 2 , mechanical strength, and pyridine adsorption desorption. These three types of extrudates exhibited different metal particle sizes and acidity. The most promising catalyst in the one-pot menthol synthesis was Ni supported first on H-Beta-38 and then extruded with attapulgite giving a 45% yield of menthols in a trickle bed reactor. This catalyst exhibited 10 nm nickel particles and a rather high amount of strong Brønsted acid sites.

One-Pot Synthesis of Menthol from Citral over Ni/H-β-38 Extrudates Containing Bentonite Clay Binder in Batch and Continuous Reactors

“…These values are low compared to the vertical and horizontal mechanical strengths of extrudates made only from bentonite in the presence of methylcellulose of 11.8 and 3.6 MPa, 39 respectively (Table S1, entry 3). At the same time, the results are on the same order of magnitude as those obtained for the ex-nitrate zeolites such as H-β-38 and H-β-25, extruded with attapulgite 23 (Table S1, entry 2) or bentonite (Table S1, entry 7), respectively, in the ratio of 7/3, exhibiting similar width and length and marginally changing after nickel insertion (Table S1, entries 2 and 6). 39 Note that bentonite extrudates as such demonstrated a rather high mechanical resistance to crushing, similar to attapulgite being more stable than a sepiolite (Table S1, entries 3−5).…”

“…The mechanical strength of extrudates was measured by the crush test using two parallel-plate Lorentzen & Wetter devices. Details about used equipment and characterization methods have been reported in our previous publication …”

“…As a comparison, in the extrudates for which Ni was loaded both on H-β-38 and on 23 (Table 3, entry 12) were applied as catalysts in citral transformations; their acidity is also given in Table 3 (entries 12, 13) for comparative purposes, indicating a lower total and BAS fraction compared to bentonite containing Ni/ H-β-38 (Table 3, entries 10, 11). Their catalytic behavior reported earlier 22,23 will be compared further with that of bentonite containing Ni/H-β-38 explored in the current work.…”

Preparation of Food Grade Superhydrophobic Coatings Based on Attapulgite Nanorods

“…Furthermore, APT is a water-rich magnesium aluminum silicate crystalline clay mineral with nanorod-like morphology. APT has received extensive attention in various fields, such as agriculture, environmental protection, cosmetics, textile printing and dyeing, food, and medicine . We have successfully prepared some superhydrophobic or superamphiphobic coatings with a good performance by constructing micro-/nanostructures using APT instead of synthetic nanomaterials. − However, these coatings aim at applications in oil/water separation, anti-icing, and anticorrosion and are not applicable to the food industry.…”

“…Attapulgite (APT), also known as palygorskite, has a reserve of about 1.4 billion tons in the world 26 a water-rich magnesium aluminum silicate crystalline clay mineral with nanorod-like morphology. APT has received extensive attention in various fields, such as agriculture, 27 environmental protection, 28 cosmetics, 29 textile printing and dyeing, 30 food, 31 and medicine. 32 We have successfully prepared some superhydrophobic or superamphiphobic coatings with a good performance by constructing micro-/nanostructures using APT instead of synthetic nanomaterials.…”